The present invention relates generally to semiconductor processing technology, and more particularly to a method for integrally forming an electrical fuse device and a metal-oxide-semiconductor (MOS) device.
An electrical fuse is a device put in a circuit as a fusable link to protect against overloading. Current above a predetermined threshold will melt the fuse and cause an open circuit. Various mechanisms can be used to program the electrical fuse device. There are three mechanisms commonly used in programming the electrical fuse device, namely, electromigration effect, silicide agglomeration and rupture. Given a certain programming current and time, the resistance of the electrical fuse can be adjusted by utilizing these mechanisms.
Conventionally, the electrical fuse device is constructed by depositing and patterning a polysilicon layer on an isolation structure separating the same from its underlying semiconductor substrate. The polysilicon layer usually comes from the same layer that is used to form the poly gate of a MOS device. This allows the electrical fuse device and the MOS device to be constructed in the same series of processing steps.
As the semiconductor manufacturing technology advances, it becomes increasingly popular that the MOS device would include a metal structure in its gate electrode. This poses a new challenge to the construction of the electrical fuse device. If separate processing steps are used to construct the MOS device and the electrical fuse device, the fabrication costs will increase. As such, it is desirable to have a method for forming an electrical fuse device and the MOS device with a metal gate structure integrally.